2008 Honda S2000 -- Chassis
8/15/2007 5:27:00 PM
The racing-inspired S2000 chassis is comprised of a front and rear double wishbone suspension, an electrically-assisted rack-and-pinion power steering system (EPS), 4-wheel disc brakes and lightweight 17-inch alloy wheels with high-performance tires. Driver aids include an Anti-lock Braking System (ABS), Vehicle Stability Assist (VSA) electronic stability control and a Tire Pressure Monitoring System (TPMS). New for 2008, firmer suspension tuning on the S2000 enhances steering feel and high speed vehicle behavior. Designed for serious, performance-minded enthusiasts, the S2000 CR takes "track-inspired" to an entirely new level with substantially firmer settings, increased body rigidity, a quicker steering ratio and "stickier" tires.
The S2000's front and rear double wishbone suspension systems are a compact in-wheel design, similar to the type used on racing cars. At each wheel, upper and lower A-shaped wishbone arms carry suspension loads directly to the subframes. Front 215/45R17 87W and rear 245/40R17 91W (255/40R17 94W on CR) tires are mounted on newly-designed and lighter weight 17-inch alloy wheels. The 11.8-inch vented front brake discs and 11.1-inch solid rear brake discs are calibrated to provide world-class stopping power and a solid, linear brake feel. Coil springs and mono-tube, gas-pressurized dampers (remote reservoirs in the rear) are used at each wheel. Stiffer front and rear stabilizers help keep body roll to a minimum.
For 2008, the S2000 suspension has been tuned with new spring, damper and stabilizer bar settings to further enhance road-holding and steering feel. The S2000 CR suspension tuning goes even further by taking advantage of body rigidity enhancements made possible with the exclusive removable hardtop configuration and by adding stiffer springs and stabilizer bars, and firmer dampers. Specially-developed steering gearbox stiffeners on the S2000 CR provides an even more direct, reflexive feel, and is further supplemented by a quicker steering ratio of 13.8:1 (compared to 14.9:1 for the S2000).
Suspension Features Summary:
- Ideal 50/50 front/rear weight distribution
- Compact "in-wheel" double wishbone front and rear suspension
- Relatively wide track (57.8 in. front/59.4 in. rear)
- Mono-tube gas-pressurized dampers
- Four-wheel disc brakes (11.8-in. vented front/11.1-in. solid rear)
S2000 CR Exclusive Features:
- Stiffer springs
- Firmer dampers
- Stiffer stabilizer bars
- Rear body brace
- Steering gear box stiffener and quicker steering ratio (13.8:1 versus 14.9:1)
- Wider rear tire size (255 versus 245)
The S2000's 50/50 front-to-rear weight distribution is considered ideal for a front-engine, rear-wheel-drive roadster. To accomplish this, and also lower the center of gravity, the engine and transmission sit low in the chassis and behind the front suspension. The S2000 is technically considered a mid-engine vehicle since the powertrain is installed behind the centerline of the front axle. The result is what engineers call a "low polar moment of inertia," which gives the vehicle a lower yaw moment - or less steering delay - which translates into quicker, more linear steering response. Since light weight is a performance asset, the S2000's various chassis components are designed to be as light and as compact as possible.
Compact In-Wheel 4-Wheel Double Wishbone Suspension
The 4-wheel, double wishbone suspension contributes greatly to the S2000's exceptional handling capabilities. The system consists of upper and lower wishbone arms at each wheel, with coil-over spring and damper units supplemented with stabilizer bars. The double wishbone design boasts many traits found on racing suspension systems that include a compact layout, highly rigid construction and low un-sprung weight. The suspension's ductile iron wishbone arms are connected to the body via rubber bushings designed to minimize vibration without compromising suspension rigidity. For 2008, the S2000 spring rates increase by 7 percent in the front and 9 percent in the rear (relative to the 2007 model.)
S2000 CR: The S2000 CR suspension tuning complements the aerodynamic balance of the vehicle with a 38 percent increased spring rate in the front and a 17 percent increased spring rate in the rear (relative to the 2008 S2000).
Mono-Tube Gas Pressurized Dampers
In addition to dampening road inputs, the S2000's mono-tube gas pressurized dampers help minimize body roll and contribute to precise weight transfer. The rear dampers, which feature large remote reservoirs, are attached to the lower wishbones, leaving more space available for the folding top and space-saver spare tire. For 2008, the S2000 damping rates increase by 10 percent in the front and 5 percent in the rear.
S2000 CR: The increased damping force of the S2000 CR damper settings are optimized for the overall more-aggressive spring rates. Compared to the 2008 S2000, the S2000 CR damping rates increase by 50 percent in the front and 32 percent in the rear.
A 27.2x5.3 mm tubular front stabilizer bar and a 25.4x4.5 mm tubular rear bar contribute to the S2000's resistance to body roll and firmly planted feel as vehicle weight transitions during cornering. The stabilizer bars connect to their respective suspension arms via ball-jointed links.
S2000 CR: The stabilizer bars are tuned to optimize the more aggressive suspension settings. The S2000 CR 28.6x4.5 front tubular stabilizer bar increases in diameter by 5 percent and decreases in wall thickness by 19 percent. The CR 26.5x4.5 rear tubular stabilizer bar increases in diameter by 4 percent and is the same thickness (relative to the 2008 S2000).
Rear Body Brace (S2000 CR-Exclusive)
Since the S2000 CR does not include the convertible soft top, the space between the rear wheels has sufficient room for a rear body brace. The substantial steel brace connects the two coil-over towers on the fender wells for added body rigidity in the rear of the vehicle. The added rigidity allows for the more aggressively-tuned rear suspension components to operate with greater precision, which helps to maximize the performance potential of the platform. Fully integrated into the body, the rear body brace installs at three locations on each side - the top of the fender well, the rear floor and to the backside of each roll bar hoop.
Electric Power Steering (EPS) System
The S2000 uses an electrically assisted power steering system in place of the more commonly used hydraulically assisted system. The electric system requires less power from the engine to operate than a hydraulic system, which ultimately benefits performance and fuel economy. The system's compactness and simplicity also offer more design freedom. The system consists of a toothed rack and pinion gear, with a microprocessor-controlled, coaxial electric motor assisting the rack. The microprocessor senses vehicle speed and steering torque and is programmed to vary boost accordingly, providing more boost at low speeds and progressively less at higher speeds. Failure warning, self-diagnosis and self-protection functions are built into the system. The S2000 has a steering ratio of 14.9:1.
S2000 CR: A quicker steering ratio of 13.8:1 and added steering gear box stiffeners give the S2000 CR a more reflexive demeanor for the race track while providing elevated levels feedback to the driver. The power steering unit's mounting has been reinforced with stiffener brackets that connect to the front of the unit, the rear of the unit, and the front subframe. The steering mount bushings' firmness has been decreased to better match the quicker steering ratio.
High-Performance, 4-Wheel Disc Braking System
The brake system is designed to deliver world class braking performance with a direct and firm pedal feel that enhances braking confidence. The heart of the system is its four large-brake disc brakes. Front rotor diameter is 11.8 inches (300 mm) and the rear diameter is 11.1 inches (282 mm). The front rotors are vented for added cooling, while the rear discs are solid. Brake rotors and calipers are cast iron. A 7.8-inch, tandem-vacuum servo-assist unit balances pedal feel (stiffness) and assist (boost). Braking bias- front-to-rear is optimized for maximum efficiency during heavy braking. The brake calipers are large, highly rigid, cast-iron units. Front piston diameter is 54 mm, and the rear pistons are 40 mm in diameter. The front pad material is Jurid632, a high-performance, low steel, fade-resistant type. Jurid632 provides high levels of frictional stability in high-temperature operating ranges, resulting in superb anti-fade characteristics. Brake-pad area is 42 square centimeters for the front pads and 27.9 square centimeters for the rear-brake pads.
4-Channel Anti-Lock Brake System (ABS)
The 4-channel ABS independently modulates braking power at each wheel. Under heavy braking, the ECU is able to detect when wheel lockup is imminent based on wheel sensor data. To prevent wheel lockup, the ABS module briefly reduces brake pressure to permit the wheel(s) to regain traction before full braking resumes.
Electronic Brake Distribution (EBD)
The EBD system electronically regulates front-to-rear brake effort proportioning via the ABS module. The system is designed to help compensate for placement of weight and maintain an optimum braking load on front and rear wheels for enhanced stopping characteristics.
Vehicle Stability Assist (VSA)
Vehicle Stability Assist is an electronic stability control system that works in conjunction with the drive-by-wire throttle and the 4-channel ABS systems to enhance controllability while the vehicle is accelerating, braking, cornering or when the driver makes a sudden maneuver. While VSA serves to effectively enhance driver control during acceleration, braking, and cornering, the system can be disabled with the touch of a button when conditions warrant it. When needed, the system functions by applying brake force to one or more wheels independently while also managing the throttle, ignition and fuel systems to help the vehicle maintain the driver's intended path of travel. The VSA system constantly analyzes data from seven sensors that monitor wheel and vehicle speed, steering input, lateral G forces and yaw rate. It compares the driver's control inputs with the vehicle's actual response. Whenever the actual response falls outside of a predetermined acceptable range, VSA intervenes with a corrective action. For instance, if VSA detects an oversteer condition, the system may apply braking force to the outside front and rear wheels to counteract the unintended yawing effect. In the event of understeer, VSA may apply braking to the inside rear wheel while reducing engine power to help return the car to its intended course.
Wheels and Tires
The S2000 features high-performance Bridgestone Potenza RE 050 215/45R17 87W front tires, mounted on 17x7.0-inch aluminum-alloy wheels. The rear tires are 245/40R17 91W and are mounted on 17x8.5-inch aluminum-alloy wheels. The wheel color is silver. A space-saver spare tire resides in the trunk.
S2000 CR: The S2000 CR features ultra high-performance Bridgestone Potenza RE 070 215/45R17 87W front tires, mounted on 17x7.0-inch aluminum-alloy wheels. The rear tires are 255/40R17 94W and are mounted on 17 x 8.5-inch aluminum-alloy wheels. The wheel color is Kaiser Silver. For weight savings, a tire sealant repair kit resides in the trunk in place of the space-saver spare tire and jack on the regular S2000.
Tire Pressure Monitoring System (TPMS)
New for 2008, a direct Tire Pressure Monitoring System (TPMS) alerts the driver when it detects that tire pressure in one or more tires drops significantly below the recommended pressure. A series of four sensors (one per tire) captures and relays information to the ECU. If the system detects that tire pressure is significantly low, a low tire pressure indicator (located in the instrument panel meter cluster) will illuminate.